Watkins, Jr. et al. U.S. Pat. No. 4,063,742 and Bill et al. U.S. Pat. No. 4,295,786 are directed to seals having compliant backing structures which provide for deformation to reduce abrasion. In the Watkins, Jr. patent the seal uses a series of thin narrow elongated metal strips to accommodate deformation while the Bill et al. patent discloses a gas path seal made of a thin layer of a deformable, metallic material such as aluminum.
Schilke et al. U.S. Pat. No. 3,817,719 discloses a porous abradable material used in gas turbine seals. The disclosed material is formed through an oxidizing step, but the resulting product is resistant to oxidation.
Panzera U.S. Pat. No. 4,080,204 describes an abradable seal for a turbine made from various alloys. The preferred alloy includes 20-27% nickel, 18-22% chromium, and 9-15% aluminum, with a trace of yttrium. The materials described in both the Panzera patent and the Schilke et al. patent can be operated only at relative low temperatures below about 2000.degree. F.